1. Field of the Invention
The present invention relates to an electroacoustic transducer which generates a sound due to electromagnetic acoustic conversion.
2. Description of the Related Art
An electroacoustic transducer has a magnetic circuit in which a magnetic field developed by a magnet passes through a base member, a magnetic core and a diaphragm and then returns to the magnet. When an oscillating electric signal is supplied to a coil wound around the magnetic core, an oscillating magnetic field is generated by the coil and then superimposed on the static magnetic field of the magnetic circuit, and vibration of the diaphragm is transmitted to the air, thereby generating a sound.
Such an electroacoustic transducer is often provided with terminals for supplying a power to the coil and connected to a wiring pattern on a circuit board by soldering in the same manner as other electronic components.
Recently, a method of performing electrical connection by using only mechanical pressing connection between a spring terminal and a circuit board is becoming widespread. According to this method, a soldering process is not necessary, thereby leading to advantages such that the heat resistance of components can be relaxed, and that steps of soldering and preprocessing for the soldering can be reduced.
As a related art, JP-A-8-321670 and JP-A-11-313394 disclose an electromagnetic sound generator having plate spring-like terminals. In a configuration in which terminals are disposed on the bottom face of the body, the height in a mounted state is increased.
JP-A-11-313393 discloses an electromagnetic sound generator having coil spring-like terminals. Lead wires of a coil are electrically connected to the terminals through a lead frame. Therefore, a soldering process must be conducted on at least four places. This may increase the number of assembly steps, and the defective ratio of the connecting portions.
The invention has been made to solve the above problems, and therefore an object of the invention is provide an electroacoustic transducer which is capable of reducing the height and size of the transducer in a mounted state and improving the reliability of mounting by means of springs.
To achieve the above object, according to the invention, there is provided an electroacoustic transducer comprising:
a diaphragm made of magnetic material;
an electromagnetic coil for supplying an oscillating magnetic field to said diaphragm;
a housing member for housing said diaphragm and said electromagnetic coil;
coil-like spring terminals which are in contact with an external circuit board for an electric connection; and
terminal accommodating portions which are opened in a bottom face of said housing member for accommodating the spring terminals;
wherein lead wires of said electromagnetic coil are directly connected to said spring terminals; and
wherein said terminal accommodating portion are sealed by a connecting process.
According to the invention, the direct connection of the lead wires of the electromagnetic coil with the spring terminals can reduce the number of connecting processes as compared with the conventional configuration in which a lead frame is interposed. Therefore, the number of assembly steps as well as the defective ratio of the connecting portions can be reduced.
In the present invention, since the terminal accommodating portions are sealed by a connecting process using solder, an electrically conductive adhesive agent or the like, the sealing property of the internal space of the component can be ensured. Therefore, foreign substances such as dust and moisture are prevented from entering the interior of the housing through the terminal accommodating portions, with the results that the life period and reliability of the component can be improved.
Also, according to the invention, the terminal accommodating portions are formed at the side of the diaphragm.
In the invention, since the terminal accommodating a portions are formed at the side of the diaphragm, the component can be so thinned as to reduce the height of the electroacoustic transducer in a mounted state.
Further, according to the invention, terminal plates are interposed between the lead wires of the electromagnetic coil and the spring terminals, respectively.
In the invention, since the terminal plates are interposed between the lead wires of the electromagnetic coil and the spring terminals, a connecting process using solder, an electrically conductive adhesive agent or the like can be easily performed, and the support strength of the spring terminals in a state where the transducer is mounted on a circuit board can be enhanced.